Poison Information | The Rhubarb Compendium The Rhubarb Compendium More than you ever wanted to know about rhubarb You are here Poison Information dan - Fri, 04/09/2010 - 19:21 Rhubarb contains oxalate, which have been reported to cause poisoning when large quantities of raw or cooked leaves are ingested. The poison in rhubarb Oxalates are contained in all parts of rhubarb plants, especially in the green leaves. There is some evidence that anthraquinone glycosides are also present and may be partly responsible. It is not clear as to the exact source of poisoning from rhubarb, possibly a result of both compounds. The stalks contain low levels of oxalates, so this does not cause problems. Chemical Composition of Rhubarb 7 - 34 mg/100g During World War I rhubarb leaves were recommended as a substitute for other veggies that the war made unavailable. Apparently there were cases of acute poisoning and even some deaths. Some animals, including goats and swine, have also been poisoned by ingesting the leaves.

The biodynamic (toxicity) mechanism by which oxalic acid works is somewhat different from organic poisons and is more analogous to heavy metal poisoning. Organic poisons often work through at the biochemical level, e.g. cyanide by interfering with respiration at the cellular level, strychnine by screwing up inter-synaptic transmission. There are many molecular substances in foods which offer no nutritional benefit, and must be processed and excreted. Oxalic acid, for example, is excreted in the urine, and its crystals are commonly found in microscopic urinalysis. Too much oxalic acid in the urine will result in kidney or bladder stones. Calcium combines with oxalic acid to form the less soluble salt, calcium oxalate, which is also found in kidney stones. Plant leaves, especially rhubarb, cabbage, spinach, and beet tops, contain oxalic acid. Oxalic acid is also found in potatoes and peas. Vitamin C is metabolized to oxalic acid; it contributes to over-saturation of the urine with crystals and possibly to stone formation.

More about Oxalic acid Oxalic acid is a strong acid of the composition HOOC-COOH, which crystallizes as the ortho-acid (HO)3 CC (OH)3 . It is sometimes also called "ethane diacid". It occurs naturally in some vegetables (like rhubarb). The can also be produced by heating sodium formate and treating the resulting oxides with sulfuric acid. It can also be obtained by the action of nitric acid on sugar, or of strong alkali's on sawdust. The product is normally traded as colorless crystals with a melting point of 101.5?C, and can be dissolved in water or alcohol. Oxalic acid reduces iron compounds, and is therefore used in metal polishes, stain removers, and writing inks. When it absorbs oxygen, it is converted to the volatile carbon dioxide and to water, and it is used as a bleaching agent, in detergents, and as a mordant in dyeing processes. How toxic is rhubarb?

0.59 - 0.72 0.39 - 0.54 From an MSDS (Material Safety Data Sheet) for Oxalic acid, LD50 (LD50 is the Median Lethal Dose, which is the dose of a drug or chemical predicted to produce a lethal effect in 50 percent of the subjects to whom the dose is given) in rats is 375 mg/kg. So for a person about 145 pounds (65.7 kg) that's about 25 grams of pure oxalic acid required to cause death. Rhubarb leaves are probably around 0.5% oxalic acid, so that you would need to eat quite a large serving of leaves, like 5 kg (11 lbs), to get that 24 grams of oxalic acid. Note that it will only require a fraction of that to cause sickness.

Symptoms of Oxalic Acid Poisoning On the body body as a whole one might experience weakness, burning in the mouth, death from cardiovascular collapse; on the respiratory system - difficulty breathing; on the eyes, ears, nose, and throat - burning in the throat; one the gastrointestinal system - abdominal pain, nausea, vomiting, diarrhea; and on the nervous system - Convulsions, coma. Precautions for rhubarb gardening Are Rhubarb Leaves Poisonous? Make a Natural Insecticide with the Leaves. Many visitors ask, " Can rhubarb leaves be composted? " It would stand to reason that if the leaves are poisonous, then adding them to compost would be a concern. However, since the oxalic acid is broken down, diluted and pH balanced quite quickly, this is not a concern. Since humans and animals do not normally ingest matter from a compost, rhubarb leaves should be able to be added safely to the compost. Go here for more information and tips for composting rhubarb leaves. Interestingly, the leaves of rhubarb can be used to make a natural insecticide.

If you have a large rhubarb patch, you may be interested in making this natural insecticide using the leaves after picking your rhubarb. A Recipe for Natural Insecticide Using Rhubarb Leaves Boil 500 grams of rhubarb leaves in a few pints of water for about 20 minutes. Allow leaf mixture to cool. Strain the liquid into a CHILD PROOF/SAFE suitable container. Add a tiny bit of dish detergent or soap flakes, (not laundry detergent). Using a spray bottle, spray on leaves to kill off bugs such as aphids and spider mites, June bugs, and fungus diseases. *NOTE - DO NOT spray this product on ANYTHING edible. Rhubarb leaves contain high amounts of oxalic acid, and are poisonous, and could cause death. If you are interested in more recipes to make simple homemade Natural Pesticides and Insecticides, Go here Here are additional pages within this website that provide helpful information about growing rhubarb in the home garden (or use the website's navigation bars): Compound Interest - Why Shouldn’t You Eat Rhubarb Leaves? – The Chemistry of Rhubarb Why Shouldn’t You Eat Rhubarb Leaves?

– The Chemistry of Rhubarb Click to enlarge Field-grown rhubarb will shortly be coming into season and appearing in supermarkets in the UK, so it seems like a good time to take a look at the chemistry behind this odd-looking vegetable. It’s mostly used in pies and desserts, but it’s only the stalks of the plant that we eat – and there’s a reason for that. This graphic takes a look at why, and also looks at the chemical compounds that contribute to the colour and the laxative effect of rhubarb. Firstly, let’s consider the poisonous nature of rhubarb leaves. It’s generally thought that this is due to the presence of a chemical compound called oxalic acid. This compound doesn’t just occur in rhubarb – it also occurs in lower amounts in spinach, broccoli, cauliflower, and brussels sprouts. Obviously, we eat those pretty regularly just fine; in vindication of the old adage ‘the dose makes the poison’, it’s the higher concentration in rhubarb leaves that poses the problem. Rhubarb leaves have a comparatively high oxalic acid content of around 0.5 grams per 100 grams of leaves.

This is present in the form of oxalic acid, and also in the form of calcium and potassium oxalate salts, and is at a level much higher than that found in other portions of the plant such as the stem. The suggested lethal dose of oxalic acid is in the region of 15-30 grams, meaning you’d have to eat a fair few kilograms of the leaves to reach this dose, but lower doses can still cause nausea and vomiting. This was discovered to the detriment of the British government in World War I, when, due to food shortages, they advocated eating rhubarb leaves. Of course, this led to cases of poisoning, and at least one death is reported in the literature . The only other study on a death due to oxalic acid poisoning was back in 1960, so the specifics of the mechanism of the poisoning are a little hazy. However, it’s known that, in the body, oxalic acid binds to calcium ions, producing calcium oxalate. Calcium oxalate is insoluble, and as such accrues in the kidneys as kidney stones. It’s not quite as clear as oxalic acid or oxalates being the culprit, though.

Some critics have pointed out that no traces of oxalates were found in post-mortem examinations of those who supposedly died from poisoning after eating rhubarb leaves, and it’s also been suggested that there may be another, as yet unidentified chemical component in the leaves of rhubarb which contributes to their toxicity. Compounds known as anthraquinone glycosides have been suggested as potential candidates, but as yet no specific compound has been identified. This leads nicely on to a discussion of some of the other compounds found in rhubarb stems, which include anthraquinones. They’re contributors to the colour of rhubarb, although not major contributors – that part is played by compounds called anthocyanins, common causes of colour in plants. The major anthocyanin in rhubarb is cyanidin-3-glucoside. A range of anthraquinones are also present, including emodin (orange), chrysophanol (yellow), physcion (red-orange), and rhein (red). Besides their colour contribution, these compounds and their derivatives also give rhubarb a laxative effect. The compounds of interest as far as these effects go are the sennosides, derivatives of anthraquinones.

During digestion, these compounds are hydrolysed into a number of smaller molecules, including rheinanthrone. It’s rheinanthrone that is thought to be the primary compound behind rhubarb’s laxative effect. Sennosides are also found in the senna plant (hence the name), and are commonly used in laxative medications. They’re included in the World Health Organisation’s list of the essential medicines. Compounds from rhubarb have also been examined for other potential medical uses. In particular, the anthroquinones have been researched as potential anticancer compounds, with both emodin and aloe-emodin having been shown to exhibit anti-tumour properties. Rhubarb: Texas Style By Skip Richter, Contributing Editor Mention growing rhubarb around a Texas gardener and youï¿½ll probably get a look something like either ï¿½whatï¿½s that?ï¿½ or ï¿½where are you from?ï¿½ Most southernersï¿½ only experience with rhubarb has been out of a can of pie filling or perhaps in one of Garrison Keillorï¿½s tall tales from Lake Wobegon.

Would you like to grow something no one else is likely to have in their gardens? Or perhaps you are a transplanted Texas immigrant from northern climes who longs for that glorious culinary delight, strawberry rhubarb pie. I have read more that once that you canï¿½t grow rhubarb down here because it is too hot! Well folks that just ainï¿½t true. You can grow rhubarb in Texas. It wonï¿½t be foolproof, but it is very do-able. First for those gardeners who are not at all familiar with rhubarb, letï¿½s get to know this new-to-us vegetable. Rhubarb is a cousin of buckwheat and garden sorrel. It is native to China where historical records dating back to about 2700 B.C. detail its use as a medicinal herb for various ailments. Marco Polo brought it to fame in the West as a medicinal plant. For a period of time in the late 1700s through early 1800s, as a result of political conflicts, Chinese emperors forbade its export to the west.

It is not until the late 1700s that we find reference to rhubarb as a food plant. By about the 1800s, it had made its way to America where it began to become a popular vegetable in northern gardens. Most rhubarb production now is centered in the states of Washington, Oregon and Michigan, although it is a popular home garden vegetable across the northern tiers of states. In these northern gardens, it is grown as a perennial and harvested from late spring through summer, depending on the location. Southern gardeners who have purchased plants (dormant roots) or otherwise tried to grow this vegetable as a perennial have failed dismally as the infernal heat of summer combines with fungal rot organisms to deal it a fatal blow. The key is to rethink the plantï¿½s traditional culture and to grow it as an annual. What we call winter here in most of Texas, rhubarb calls sporadic cold snaps. It can be grown in most of the state from August to May and then discarded to make room for a heat-loving vegetable.

You can also purchase roots and plant them as soon as the companies will dig and ship them, but this is much more expensive as they still will be only annual plants for us. So here are the basics of how to grow rhubarb from seed in our southern climate. In mid- to late August plant seeds of rhubarb indoors. Most rhubarb varieties are vegetatively propagated and sold as dormant roots, but one called ï¿½Victoriaï¿½ is readily available from seed. I have also grown a variety called ï¿½Glaskinï¿½s Perpetualï¿½ but found ï¿½Victoriaï¿½ to be just as good or perhaps a little better. Soak the seeds in warm water for a few hours prior to planting. Then fill 4-inch pots with a good potting or seed starting mix. Place two seeds in each pot (to hedge your bet) and cover them about 1/4 inch deep with the mix and moisten. Keep them indoors at room temperature until they sprout, when they will then need to be placed in a very bright window. Once the seedlings are up and on their way they can be moved to a bright shady outdoor location.

Keep the soil moist but take care not to keep them soggy wet. When they are a week old, start fertilizing with a dilute liquid solution each time you water them. Soon afterward move them to a brighter location with some morning sun. Prepare the garden soil well prior to setting the transplants out into the garden. Rhubarb is fairly tolerant of a wide soil pH range. I have seen it do well in the acid sands of East Texas and the high pH clays of Central Texas. It is beneficial, however, to mix several inches of compost into the soil and to plant in raised beds to facilitate drainage. The plants respond well to fertilization, so select a 3-1-2 or 4-1-2 ratio product (such as 8-2-4 or 15-5-10) and mix in 2 to 4 cups (depending on strength of the product) per 100 square feet of garden bed area prior to planting. After the young plants are about 4 inches tall or have three to five leaves you can plant them out into the garden. This will be in about late September or early October.

If the weather is still hot, a makeshift shade structure over them will help a lot to get them through the transition. One easy technique is to cut a bamboo shoot or a small juniper branch with leaves attached and stick it into the ground on the west side of the plant, leaning over it a bit, to provide filtered shade. Within a few weeks as the heat begins to ease up a bit, the plants will be acclimated better and ready to take off on their own. During this transition time watering is critical. The plants need to stay fairly moist, but not soggy wet. Rhubarb is susceptible to several fungal rots and if you overwater the plants, they will quickly succumb to stem and crown rots, and die. As the weather moves into the mild days of fall, rhubarb plants will slowly start to take off. Fertilize them monthly from September through April with 1 cup of the same product used prior to planting per 100 square feet. While the plants can take considerable cold, a hard freeze will damage the aboveground leaves and petioles. For this reason some protection on very cold nights is worthwhile.

Milk jugs for small plants or clear plastic tunnels for larger plants in rows can protect the above ground parts and give you a head start on the spring season. By late winter to spring the plants will resume rapid growth. This is the time when harvest may begin. In Texas, rhubarb reaches a respectable size by about March or April and can be harvested on through May. The edible portions of the plant are the elongated and thickened leaf stalks. Grasp a leaf stalk and pull sideways. They break off easily. Or if you wish, you can cut them off. Immediately trim off the leaves leaving just the stalk. Then take the stalks inside to wash and refrigerate them. I prefer to harvest in the morning as the leaves wilt rapidly in the heat of the day. I should note here that only the stalks are to be eaten, NOT the leaves on the end of the stalks. Rhubarb leaves contain oxalic acid at levels that can be poisonous. However, while the leaves contain high concentrations of this compound, the levels found in the stalks are very low and not considered hazardous.

For that matter, oxalic acid is also found in low levels in many other vegetables we eat including spinach, cabbage, beet greens, and to some degree potatoes and peas. Some references indicate that stalks with cold damage (soggy soft areas) or those with significant frost damage to their leaves should also be avoided, but this situation is more common on fall harvested rhubarb in the north and is generally not seen here in Texas during our spring harvest time. Our Texas-grown rhubarb will generally be more green than red in color. This is partially due to our warm climate, partially because the reddest varieties are not available from seed, and also because our Texas plants are seedlings and therefore have considerable genetic variability. But they are quite productive and the quality is fine. Rhubarb is not eaten fresh but rather is cooked in pies, tarts and sauces. The most famous dish of course is strawberry rhubarb pie. By a fortuitous coincidence only explained as Divine design our Texas rhubarb season and strawberry season run concurrently. So you can plant a strawberry-rhubarb patch this fall and enjoy a great harvest in spring.

For a wealth of information on using rhubarb in great culinary creations and many wonderful recipe ideas, check out the following Web site: #TOC46 . If you go overboard and need some help canning or freezing your rhubarb harvest, this Web site will be very helpful: . So if you are a bit adventurous and like to try new things in the garden consider adding some rhubarb to your fall gardening plans. Does Rhubarb Deserve Its Killer Reputation? | National Geographic | The Plate Rebecca Rupp Photograph by Erika Larsen, National Geographic Although rhubarb leaves can grow quite large, as shown by the winner of the annual contest at the Rhubarb Festival in Lanesboro, Minnesota, they are definitely not something to eat. May 18, 2016 Does Rhubarb Deserve Its Killer Reputation? by Rebecca Rupp Rhubarb is next to impossible to kill. Here in northern Vermont, rhubarb is about the first thing that pops up in our garden in the spring—and that’s not due to us; over the years, we’ve inadvertently squashed it, stepped on it, weed-whacked it, and even mowed it down with the tractor. And still it survives.

Rhubarb is tough. In my experience, it’s the botanical equivalent of The Cat Came Back . This may have something to do with rhubarb’s chilly center of origin in east Asia—most likely, botanists guess, in inhospitable Mongolia. Marco Polo, on his famous 13th-century journey to Cathay, noted it growing “in great abundance” in the mountains of northwest China. Today it thrives in Siberia, Canada, Alaska, Michigan, and Maine, none of which is noted for climates for the faint-hearted. While rhubarb seldom makes anybody’s favorite fruit list (it’s not a fruit, but we treat it that way), should we be socked with a new ice age , indomitable rhubarb will almost certainly still be around. Children pose as rhubarb at the annual Rhubarb Festival in Lanesboro, Minnesota. Photograph by Erika Larsen, National Geographic Like eggplant and bitter melon, rhubarb was first adopted by the Chinese as a medicine: ancient Chinese and, later, Greeks and Romans all used the dried roots as a laxative. The Romans may have imported theirs from Russia.

Rhubarb’s scientific name, Rheum rhabarbarum, is said to derive from the Latin Rha, the ancient name for the Volga River, whose banks were once a rich source of rhubarb, and barbarum, meaning barbarous, which shows what the Romans thought of the Tartars. During the medieval period, it was imported into Europe from Asia via the Silk Road; upon arrival, it cost even more than such pricey substances as cinnamon, saffron, and opium. Nobody considered actually eating rhubarb for another several centuries—and perhaps sensibly so, since the leaves are poisonous and the raw red or green stalks are sour enough to set teeth on edge. The chemical villain in rhubarb leaves is oxalic acid, a compound also found in Swiss chard, spinach, beets, peanuts, chocolate, and tea. Chard and spinach, in fact, contain even more oxalic acid than rhubarb—respectively, 700 and 600 mg/100 g, as opposed to rhubarb’s restrained 500.

Rhubarb’s killer reputation apparently dates to World War I, when rhubarb leaves were recommended on the home front as an alternative food. At least one death was reported in the literature, an event that rhubarb has yet to live down. Oxalic acid does its dirty work by binding to calcium ions and yanking them out of circulation. In the worst-case scenario, it removes enough essential calcium from the blood to be lethal; in lesser amounts, it forms insoluble calcium oxalate, which can end up in the kidneys as kidney stones. In general, however, rhubarb leaves don’t pose much of a threat. Since a lethal dose of oxalic acid is somewhere between 15 and 30 grams, you’d have to eat several pounds of rhubarb leaves at a sitting to reach a toxic oxalic acid level, which is a lot more rhubarb leaves than most people care to consume. People first bought into rhubarb as a food plant in the early 1800s, when British plant breeder Joseph Myatt discovered that—diced, stewed, and laced with lots of sugar—sour rhubarb stalks could be rendered scrumptious.

In 1837, the year of Queen Victoria’s coronation, he followed this up by introducing a new, sweeter, and notably delicious rhubarb cultivar, which he named “Victoria” in honor of the new young queen. (For would-be growers, Victoria rhubarb is still available .) Rhubarb cookery was soon all the rage, with a proliferation of recipes that included rhubarb tarts, compotes, fools , cakes, custards, jams, jellies, and wine. Like celery, the rhubarb stalk is actually a petiole, a chunky, beefed-up version of the skinny sub-stem that connects a leaf to its parent branch. This, incidentally, means that rhubarb, botanically, is a vegetable, rather than fruit, which last results from the fertilized ovary of a flower. (See Is a Tomato a Fruit? ) Edible parts of plants that are not fruits are deemed vegetables, such as leaves (lettuce), roots (carrots), stems (asparagus), and petioles (rhubarb).

In spite of biology, however, in 1947, a New York court ruled that rhubarb was a fruit, based on its common culinary use in dessert, as in strawberry-rhubarb pie . Benjamin Franklin is generally credited with introducing rhubarb to America, since he shipped some samples to American botanist John Bartram in 1771, though at the time, Franklin was clearly thinking of rhubarb in terms of medicine, not pie. Alternatively, Thomas Jefferson may have brought edible rhubarb to American gardens, though here even the usually precise Jefferson is confusing, describing “esculent rhubarb” with “leaves excellent as Spinach.” In other words, whatever he was eating, it sounds like salad, not stewed rhubarb stalks. By the 1830s, however, rhubarb, sweetened and stewed, had clearly caught the public fancy, since its common American nickname was “pie plant,” from its popularity as an ingredient in pies.

One mid-century cookbook describes “Rhubarb or Pie Plant” as “the greatest of spring luxuries” but warns about the price of added sugar: “for stewing or pies, no spice is required, but sugar may be put in as long as your conscience will let you, and a handful afterwards.” Today, polls show that the all-American apple still rules the roost as the country’s favorite pie—but a springtime strawberry-rhubarb often comes in second best, nudging out pumpkin, cherry, blueberry, and key lime. A Modern Herbal | Rhubarbs [ Top ] [ Top of Rhubarb, Turkey ] ---Part Used--- The root, scraped or rasped, halved longitudinally when very large, and then cut into transverse pieces and strung on cords to dry in the sun, the drying afterwards being completed by stove heat. It is dug in October. Chinese or Turkey Rhubarb occurs in commerce in brownish-yellow pieces of various size, usually perforated, the holes often containing a portion of the cord used to hang the sections of the root on during drying. The outer surface is generally powdery (the bark having been removed) and shows a network of white lines.

The taste is astringent and nauseous, and there is a characteristic odour. The preparations used in medicine are: the powdered root, a fluid extract, a tincture, syrup, infusion and solution. It is also employed as a principal ingredient in compound powder (Gregory's Powder) and in compound pills. [ Top ] [ Top of Rhubarb, Turkey ] ---Constituents--- The chemical constituents of Rhubarb root are not yet completely known. Recent investigations indicate that the most important constituents are a number of substances which may be divided into two groups, viz. tannoid constituents and purgative constituents, several of which have been isolated in a free state: the former are astringent and the latter laxative. Three crystalline tannoids have been extracted. The purgative constituents apparently exist in the form of an unstable crystalline substance: Rheopurgarin. This splits up into four glucosides: two of these yield Chrysophanic acid (so named from its forming yellow crystals) and Rheochrysidin respectively. The other two glucosides have not yet been isolated, but they appear to yield Emodin and Rhein.

There are also several resinous matters, one of which, Phaoretin, is purgative, and mineral compounds are also present, especially Oxalate of Calcium. The astringency of Rhubarb is due to a peculiar tannic acid (Rheo-tannic), which is soluble in water and alcohol. [ Top ] [ Top of Rhubarb, Turkey ] ---Medicinal Action and Uses--- Astringent, tonic, stomachic, aperient. In large doses, Rhubarb powder acts as a simple and safe purgative, being regarded as one of the most valuable remedies we possess, effecting a brisk, healthy purge, without clogging the bowels and producing constipation, too often consequent upon the use of the more active purgatives. It is especially useful in cases of diarrhoea, caused by an irritating body in the intestines: the cause of irritation is removed and the after-astringent action checks the diarrhoea. The following note from The Chemist and Druggist of March 31, 1923, supports this: 'Rhubarb in Bacillary Dysentery.

- An investigation was undertaken to determine the way in which rhubarb acts in this disease and which constituent was responsible for its action, one writer having stated in regard to the treatment of bacillary dysentery that no remedy in medicine has such a magical effect. (Lancet, I, 1923, 382.) A solution containing all the purgative constituents of rhubarb soluble in water (1 gr. of B.P. rhubarb extract) was allowed to act on B. dysenterial Shiga and Flexner of the bacillus No. 1 of Morgan without affecting growth in the broth tubes. Fresh undiluted ox bile has not distinct action on the bacilli, thus indicating that the therapeutic effect of rhubarb is not due to its cholagogue action. Neither does the serum of a rabbit treated with rhubarb have any germicidal action. The nature of the therapeutic effect of rhubarb in bacillary dysentery therefore still remains obscure.' And again, September 3, 1921, in the Lancet, by Dr. R. W. Burkitt: 'In the former journal, Dr. R. W.

Burkitt, of Nairobi, British East Africa, states that acute bacillary dysentery has been treated in that colony almost exclusively with powdered rhubarb for the past three years. The dose given has been 30 grains every two or three hours until the rhubarb appears in the stools. After a few doses the stools become less frequent, haemorrhage ceases, and straining and the other symptoms of acute general poisoning, which characterize the disease, rapidly disappear. In children 5 grains is given every two hours for three doses only, as, if the administration is continued longer, the drug will cure the dysentery, but produce an obstinate simple diarrhoea. In both adults and children the thirst is combated by small, frequent doses of bicarbonate of soda and citrate of potash. Dr. Burkitt concludes: "I know of no remedy in medicine which has such a magical effect. No one who has ever used rhubarb would dream of using anything else.

I hope others will try it in this dreadful tropical scourge." ' Rhubarb in small doses exhibits stomachic and tonic properties, and is employed in atonic dyspepsia, assisting digestion and creating a healthy action of the digestive organs, when in a condition of torpor and debility. The tincture is chiefly used, but the powder is equally effective and reliable. Rhubarb when chewed increases the flow of saliva. [ Top ] [ Top of Rhubarb, Turkey ] ---Preparations and Dosages--- Powdered root, 3 to 30 grains. Comp. powder, B.P. (Gregory's), 20 to 60 grains. Comp. pill, B.P., 4 to 8 grains. Solid extract, U.S.P., 4 grains. Solid extract, B.P., 2 to 8 grains. Tincture comp., B.P., 1/2 to 4 drachms. Tincture, U.S.P., 1 drachm. Tincture aromat., U.S.P., 1/2 drachm. Fluid extract, 10 to 30 drops.

Syrup, B.P., 1/2 to 2 drachms. Infusion, B.P., 1/2 to 1 OZ. Syrup, B.P. and U.S.P., 1/2 to 2 drachms. Arom. syrup, U.S.P., 2 drachms. Rheum, 1 to 4 grains. [ Top ] [ Top of Rhubarb, English ] ---Cultivation--- Rhubarb may be raised from seed, but it is better and more usual to obtain established roots. Seeds may be sown, however, in drills a foot or more apart, in the open, from March to April, and the young plants thinned out to 10 inches, transplanting them in the autumn, allowing about 4 feet every way to each plant. Rhubarb roots may be planted at any time of the year, although mild weather in autumn or early spring is best; it should be planted on a clear, open spot, on good soil, which should be well trenched 3 feet deep, and before planting, a good substance of rotten manure should be worked into the soil.

When the plants are to be increased, it is merely necessary to take up large roots and divide them with a spade: every piece that has a crown to it will grow. Fresh plantations are generally made in February or March, but Rhubarb may still be divided early in May. To ensure fine rhubarb for table use, a large dressing of well-rotted manure should be dug in about the roots as soon as the last of the leaves have been pulled. It is not right to wait until the winter, before the plants are dressed. Old roots ought to be divided and replanted every fourth or fifth year, when the plants are grown for the use of the stems. If Rhubarb be forced on the ground where it grows, nothing more is required than to cover with large pots, half casks, or boxes, round and over which should be placed plenty of stable manure. Roots forced in greenhouse or in frames do not need to have the light excluded from them. Such roots, however, require dividing and replanting in the spring out of doors.

[ Top ] [ Top of Rhubarb, English ] ---Part Used Medicinally and Preparation--- The roots of English Rhubarb are generally taken from plants from four years old and upwards. They are dug up in October, washed thoroughly and the fibres taken away. The bark of English Rhubarb is not usually removed. The roots of both R. Officinale and R. Rhaponticum are much smaller than those of the Chinese Rhubarb and are easily distinguished by their distinctly radiate structure. They are also more shrunken, more or less distinctly pink in colour, and have a diffuse circle of isolated star-spots on the transverse section. The roots of R. officinale cultivated in England resemble Chinese Rhubarb, but are more spongy, and shrink and wrinkle as they dry, and are softer to cut. They have a less rich colour than the Chinese, and have no network of white lines on the outer surface, the dark red and white lines usually running parallel to each other and the star-spots being less developed, fewer and more scattered. The English Rhubarb from R. Rhaponticum shows red veins, that of R.

officinale is usually in larger pieces and has blackish veins. The root is used as a drug in powdered form. [ Top ] [ Top of Rhubarb, English ] ---Constituents--- Root. The constituents of R. officinale are similar to those of Chinese Rhubarb. Rhapontic or Garden Rhubarb contains no emodine, rhein or rhabarberine, but has in it a crystalline body, rhaponticin. Stem and Leaves of R. Rhaponticum. Potassium oxalate is present in quantity in Rhubarb leaf-stems, and certain persons who are constitutionally susceptible to salts of oxalic acid, show symptoms of irritant poisoning after eating rhubarb stewed in the ordinary manner. Many people of a gouty tendency do well to avoid it, and those subject to urinary irritation should take it very sparingly or not at all. Rhubarb stems did not come into general use as a substitute for fruit till about 100 years ago.

We hear of a pioneer grower, Joseph Myatt, of Deptford, sending, in 1810, five bunches of Rhubarb to the Borough Market and only being able to dispose of three. But he persevered in his efforts to make a market for Rhubarb, raised improved varieties, and a few years after, Rhubarb had become established in public favour as a culinary plant. It was, however, soon realized that the use of Rhubarb as food was sometimes attended with some risk to health. Lindley, in his Vegetable Kingdom, 1846, remarks that oxalic acid exists in both Docks and Rhubarb, and that the latter contains also an abundance of nitric and malic acid, and goes on to say that whilst these give an agreeable taste to the Rhubarb when cooked, he considers them illsuited to the digestion of some persons.

The Penny Cyclopaedia, 1841, warned persons subject to calculous complaints against eating Rhubarb stalks, owing to the presence of oxalic acid, stating that 'the formation of oxalate of lime, or mulberry calculus, may be the consequence of indulgence.' The chemical constituents of Rhubarb leaves were till recently not fully ascertained, but the analysis has lately been undertaken under orders from the Home Office, in consequence of fatal and injurious effects having resulted from eating the leaves cooked as spinach. The report of the official analyist states that the leaves contain some 0.3 per cent oxalates of potassium and calcium oxalates. It is possible that the recent cases of poisoning occurred in subjects specially susceptible to oxalic poisoning, as there are also many cases reported of no harm ensuing from a use of Rhubarb leaves as a vegetable. In Maunders' Treasury of Botany Rhubarb leaves are mentioned as a pot-herb.

Green (Universal Herbal, 1832) says: 'The leaves are also used by the French in their soups, to which they impart an agreeable acidity, like that of Sorrel.' Reference has recently been made in the press to a letter which appeared in the Gardeners' Chronicle for 1846, in which the gardener of the Earl of Shrewsbury at Alton Towers, Staffordshire, told how rhubarb leaves had been used there for many years as a vegetable. He also mentioned that the flower of the plant (before the leaves expanded) could be used like broccoli. A subsequent note by him makes it clear, however, that the leaf-stems were meant, for he then says: 'I have no experience in the eating of the leaves and think them nauseous to the taste and unpleasant to the smell.... I tasted them boiled and they did not appear to me to have one redeeming feature....' The flower of the plant, when in bud form, has been eaten as a pleasant substitute for broccoli; when cooked au gratin, with white sauce over it, the cheese quite obviates any bitterness of taste.

Further reference to the Gardeners' Chronicle, of 1847, shows records of the varying results of eating the young inflorescence, producing no ill-effects in some cases and serious illness in others, and a case is recorded of severe sickness attacking a whole family after partaking of the leaves boiled as a vegetable. In 1853 we find the question again raised. In 1872 we hear of deaths from eating the leaves in America, and in 1899 we find a revival of interest in Rhubarb leaves as a vegetable, quite opposite opinions being expressed in a correspondence in the gardening papers. In 1901 we hear of a man dying after eating stewed Rhubarb leaves, the verdict at the inquest being: 'Accidental death, caused by eating rhubarb-leaves.' It was stated then that the leaves were used as a vegetable in parts of Hampshire. The British Medical Journal in December, 1910, mentions several cases of rhubarb poisoning. The leaves are sometimes made use of in the fabrication of fictitious cigars and tobacco.

The shape of the hairs, however, as seen under a microscope, can enable the observer to detect the presence or absence of tobacco, but it is not so easy to determine the source of the fraudulent admixtures. It is possible that the chemical composition of Rhubarb varies to some extent according to the variety and the soil on which it is grown. It has been stated that the amount of water present is less when the plants are grown on poor soil, while the acid principle is more abundant. As regards the method of cooking, the British Medical Journal points out that hard water would precipitate the oxalate, while a soft water might leave it in the form of soluble oxalate, more readily assimilated into the systems of those susceptible to this kind of poisoning. In a recent case that terminated fatally, the leaves were well washed, drained, cut up and put into boiling water, in an iron saucepan, for 20 minutes. A little salt and kitchen soda were added, but nothing else. Being acid, the leaves should, of course, not be cooked in a copper vessel.

---Medicinal Action and Uses--- Though the English Rhubarb root is milder as a purgative, it is more astringent, and has been considered a better stomachic than the foreign. It is specially useful in infantile stomach troubles and looseness of the bowels. In fairly large doses it acts as a laxative. Dose of powdered root, 5 to 60 grains. The dose is entirely individual, 12 grains acting on some persons, as much as 20 on others of the same age. It has been held that 20 grains of the seed are equal to 30 of the root, as regards purgative power. The properties of the seeds are similar to those of the root. A decoction of the seeds is supposed not only to ease pains in the stomach, but to strengthen it by increasing the appetite. A strong decoction of the root has been employed as a good w ash for scrofulous sores. If a portion of the root be infused in water, and when strained a few grains of salt of tartar be added, a very beautiful red tincture results, which might prove valuable for the purposes of a dye.

Culpepper says of Rhubarb: 'If your body be anything strong, you may take 2 drams of it at a time being sliced thin and steeped all night in white wine, in the morning strain it out and drink the white wine; it purges but gently, it leaves a binding quality behind it, therefore dried a little by the fire and beaten into powder, it is usually given in Fluxes.'

Question: Which acid is found in the leaves of Rhubarb?
Answer: OXALIC ACID